TAKAMORI AKIRA, TAKENAKA NAOKI, HASE NOBUYASU · Institutional Repository of Xi'an Institute of Optics and Fine Mechanics, Chinese Academy of Sciences (Xian Institute of Optics and Precision Mechanics) · 1989
PURPOSE:To execute a distributed feedback operation of a beam without being influenced by a shape of a diffraction grating by a method wherein, because the diffraction grating of a semiinsulating thin film is formed and a region where an injected electric current flows is limited regularly, the diffraction grating by a change in a composition is not formed. CONSTITUTION:An Fe-doped semiinsulating InGaAsP layer 22 is grown on an n-InP substrate 21; a resist 23 is coated and a diffraction grating pattern 23 is formed; after that, an etching operation reaching the n-InP substrate 21 is executed; a semiinsulating InGaAsP diffraction grating 24 is formed. The resist 23 is removed; after that, an n-InGaAsP guide layer 25, an undoped InGaAsP active layer 26, a p-InP clad layer 27 and a p-InGaAsP cap layer 28 are grown; an n-type electrode 29 and a p-type electrode 30 are evaporated. An electric current injected from the side of the n-type substrate 21 reaches the active layer 26 after a current path 31 has been modulated by the diffraction grating 24; a refractive index corresponding to a cycle of the diffraction grating is distributed.
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KAMITE KIYOTSUGU · Institutional Repository of Xi'an Institute of Optics and Fine Mechanics, Chinese Academy of Sciences (Xian Institute of Optics and Precision Mechanics) · 1989
PURPOSE:To inhibit oscillations in a Fabry-Perot mode and a TM mode at the time of direct modulation with a relaxation oscillation by a method wherein the reflectivity on a first end face of a laser is made smaller than the resistivities on a second end face of the laser and is set within a prescribed range. CONSTITUTION:An n-type InP substrate 11, a p-type InP layer 12, an n-type InP layer 13, a p-type InGaAsP layer 14, an InGaAsP waveguide layer 15, an InGaAsP active layer 16 and a diffraction grating 17 formed in the substrate 11 are provided. The end face 22 of end faces 21 and 22 of a DFB(Distributed Feed Back) laser is a cleavage plane and a low reflectivity film 23 having a 0.1-4% reflectivity on the side of the end face 21 is formed on the other end face 2 Thereby, an oscillation in a Fabry-Perot mode and a TM mode at the time of direct modulation with a relaxation oscillation can be inhibited and at the same time, it can be prevented that an error floor is generated in the transmission characteristics of the laser.
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YAMAUCHI HIDEKI · Institutional Repository of Xi'an Institute of Optics and Fine Mechanics, Chinese Academy of Sciences (Xian Institute of Optics and Precision Mechanics) · 1991
PURPOSE:To prevent the end face of a resonator from being broken even in case a light density is high and to contrive the speedup of a distributed feedback laser by a method wherein a light density in the central part of the resonator is made relatively higher than that in the vicinity of the end face of the resonator. CONSTITUTION:A buffer layer 2, a clad layer 3, an active layer 4, a barrier layer 5 and a guide layer 6 are continuously grown in order on a substrate Then, a secondary diffraction grating 11 is formed in the layer 6 by an interference exposure and a chemical etching. At this time, the depth of etching is adjusted so that the product of a resonator length and a coupling coefficient is a prescribed value. Thereby, a light density in the central part of a resonator becomes relatively higher than that in the vicinity of the end face of the resonator, a breaking of the end face is never generated, the upper limit of a modulated frequency is not restricted and a distributed feedback laser can be speeded up.
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WESTBROOK, LESLIE DAVID · Institutional Repository of Xi'an Institute of Optics and Fine Mechanics, Chinese Academy of Sciences (Xian Institute of Optics and Precision Mechanics) · 1995
Improved single-modedness is achieved in distributed feedback (DFB) lasers by minimising the feedback provided at or near the ends of the DFB grating. The feedback may be minimised at one or both ends of the grating. Feedback is controlled by reducing the coupling to the grating. Coupling is reduced by reducing the depth of the grating's teeth and/or by increasing the spacing between adjacent teeth.
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Evans, G. A., Elachi, C., Yeh, C. · NASA Technical Reports Server (NASA)
Utilizing round optical fibers as communication channels in optical communication networks presents the problem of obtaining a high efficiency coupling between the optical fiber and the laser. A laser is made an integral part of the optical fiber channel by either diffusing active material into the optical fiber or surrounding the optical fiber with the active material. Oscillation within the active medium to produce lasing action is established by grating the optical fiber so that distributed feedback occurs.
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MUROYA, YOSHIHARU · Institutional Repository of Xi'an Institute of Optics and Fine Mechanics, Chinese Academy of Sciences (Xian Institute of Optics and Precision Mechanics) · 2000
A stable single-mode oscillation semiconductor laser is obtained by flattening the distribution of electric field intensity in the direction of the resonator axis, and to provide a distributed-feedback semiconductor laser generator having a more satisfactory difference in threshold gain between the principal and subsidiary modes. The laser includes an active layer which radiates light as a result of the injection of electrons, a light guide layer which is next to this active layer guides light emitted from the active layer, a plurality of semiconductor layers between which the active layer and light guide layer are interposed, electrodes which permit electrons to be injected from these semiconductor layers into the active layer, a non-reflective coating provided on both ends of the active layer in the direction of oscillation, and a diffraction grating which is provided on the light guide layer for selecting the oscillatory wavelength of the light. The diffraction grating has a plurality of uniform pitch areas formed with a uniform and equal pitch, and a varying pitch area interposed between the uniform pitch areas and having a plurality of pitches longer and shorter than those of these uniform pitch areas, the latter serving to select the oscillatory wavelength of the light, where the absolute value of the sum-total of the amount of phase change in the varying pitch area (cumulative amount of phase change) in relation to the phase in the uniform pitch areas is between 3/2 and 11/2 times the pitch of the diffraction grating of the uniform pitch areas.
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R. L. Fork, K. R. German, Edwin A. Chandross · Applied Physics Letters · 1972
A tunable (0.567–0.605 μ) solid-state dye laser with a small active volume (10 μ×80 μ×1 cm), which uses a nondestructively read-reversible optical-memory material to control the intensity and wavelength of the laser emission, is described. The optical-memory material, photodimers of acridizinium ethylhexanesulfonate, provides distributed feedback in the form of an adjustable-period phase grating which can be optically written (0.364 μ) or erased (0.313 μ). Reproducibility of laser switching, time and spectral structure, and operation at low temperatures where photodegradation of the dye is significantly reduced are discussed.
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KUWAMURA YUJI · Institutional Repository of Xi'an Institute of Optics and Fine Mechanics, Chinese Academy of Sciences (Xian Institute of Optics and Precision Mechanics) · 1988
PURPOSE:To reduce noises induced by returning light, by adding first and second Bragg reflection regions, in which the gain in an optical waveguide layer is always zero or less than zero. CONSTITUTION:In a laser light emitting region 1, a diffraction grating 5-1, whose phase is inverted into an approximately central position in the direction of resonant axis, is provided, and the gain of active layer 7 is more than zero. In first and second Bragg reflection regions 2 and 3, diffraction gratings 5-2 and 5-3, whose phases agree and are continued at both ends of the region 1, are provided, and the gain in an optical waveguide layer is always less than zero. Non-reflecting films 4-1 and 4-2 are provided at end surfaces. Electrodes 2a and 3a are provided so that the Bragg reflection regions 2 and 3 are made to be transparent regions for light having a laser oscillating wavelength and so that a constant current is injected and the gain becomes almost zero. Noises induced by returning light are reduced by reflecting part of the returning light in the Bragg reflecting regions and by increasing the electric field strength at the laser light emitting part.
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UTAKA, KATSUYUKI, SAKAI, KAZUO, AKIBA, SHIGEYUKI · Institutional Repository of Xi'an Institute of Optics and Fine Mechanics, Chinese Academy of Sciences (Xian Institute of Optics and Precision Mechanics) · 1986
A semiconductor laser of distributed feedback type, which is provided with a portion having periodic refractive index variations in the direction of light propagation in one of an active layer and a layer adjacent thereto and is caused to perform laser oscillation by injecting a current into the active layer portion. In accordance with the present invention, a current injection region having no periodic refractive index variations is formed on an extension of the portion having the periodic refractive index variations.
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SAKUMA ISAMU · Institutional Repository of Xi'an Institute of Optics and Fine Mechanics, Chinese Academy of Sciences (Xian Institute of Optics and Precision Mechanics) · 1989
PURPOSE:To prevent the diffusion of carrier injected in an active layer, and enable the confinement of the carrier, by forming a sufficiently large difference of forbidden bandwidth between the active layer and a clad layer. CONSTITUTION:On an n-InP substrate 1, the following layers are continuously subjected to liquid growth; a 4mum thick n-InGaAsP optical guide layer 2, an n-InP clad layer 3, a 3mum thick InGaAsP active layer 4, a P-InP clad layers 5, and a 1mum P-InGaAsP cap layer 6. The typical thickness of each layer is as follows; the optical guide layer 2 is 0.08mum, the n-clad layer 3 is 0.05mum, the active layer 4 is 0.1mum, the P-clad layer 5 is 5mum and the cap layer 6 is 3mum. Finally a P-side electrode 8 and an N-side electrode 9 are formed.
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MITO IKUO · Institutional Repository of Xi'an Institute of Optics and Fine Mechanics, Chinese Academy of Sciences (Xian Institute of Optics and Precision Mechanics) · 1988
PURPOSE:To stabilize laser operation over the high-output range, by regulating the phase shift amount of a diffraction grating so as to be smaller than a specified value. CONSTITUTION:A diffraction grating 100 is formed on a (001)-plane n-type InP substrate 1 so that a phase shift part 111 is formed in the center of a resonator. The amount of phase shift in the phase shift part 111 is set up to be pi/2 pitch or less of the diffraction grating. Successively, a n-InGaAsP light-guide layer 2, a non-doped InGaAsP active layer 3, and a p-InP clad layer 4 are piled on the n-InP substrate Grooves 51 and 52 are formed to interpose a meta-stripe 50. Both of a p-type InP current-blocked layer 5 and a n-type InP current-locked layer 6 are formed not to be piled on the upper surface of the meta-stripe 50, besides with a p-InP embedded layer 7 and a p-InGaAsP cap layer 8 being piled thereon. After the n-InP substrate 1 being polished, both evaporation and heat treatment of Cr/An as an electrode 130 and of Au/Ge/Ni as an electrode 131 are respectively performed. Successively, cleaving operation is performed to obtain a 300mum-long resonator, and then evaporation of low- reflection films 120 and 121 made of SiNx is performed. Hence, an element having stable operation in a single axial mode can be obtained with high yield.
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KINOSHITA JUNICHI · Institutional Repository of Xi'an Institute of Optics and Fine Mechanics, Chinese Academy of Sciences (Xian Institute of Optics and Precision Mechanics) · 1988
PURPOSE:To enable a distributed feedback laser to oscillate in a uniaxial mode up to a high output level, by correcting an equivalent refractive index or diffraction grating cycle of a region having intense optical intensity distribution so as to be smaller than that of a region having weak optical intensity distribution. CONSTITUTION:Diffraction grating 12 having lambda/4 phase shift is formed on an n-type InP substrate 1 Then, an n-type 3 mum GaInAsP optical waveguide layer 13, an undoped 55 mum active layer 14, a P-type InP clad layer 15 and ptype GaInAsP contact layer 16 for example are deposited in that order by means of liquid-phase epitaxy. The width of the optical waveguide stripe including the active layer is varied by means of an appropriate mask, exposure and mesa etching such that the width of a region 17a having a smaller distance between the lambda/4 phase shift position 12a and the cleaved face is smaller than the width of a region 17b having a larger such distance, by about o.15 mum for example. A BH (buried hetero) structure is provided and p electrode 19 and an n electrode 20 are formed. This element is then cleaved such that the lambda/4 phase shift position 12a is deviated from the center of the length of a resonator of 300 mum by 30 mum for example. Si3N4 single-layer films are applied on the opposite end faces.
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SCIFRES DONALD R., BURNHAM ROBERT D. · Institutional Repository of Xi'an Institute of Optics and Fine Mechanics, Chinese Academy of Sciences (Xian Institute of Optics and Precision Mechanics) · 1979
ABSTRACT OF THE INVENTION A laser having layers of a first material inter- leaved with layers of a second material with the first material having a different index of refraction and band- gap than those of the second material. The thicknesses of the layers of the first and second materials satisfy the relationship t = where m is the laser mode and n is the index of refraction of the material, such that the right and left going waves of the light produced by the layers of the first material when the laser is pumped are coupled and reinforced in a coherent manner by the layers of the second material such that reflections from the second material are in phase, thus allowing laser operation in the absence of discrete end mirrors.
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HIRAYAMA YUZO, FURUYAMA HIDETO, OKUDA HAJIME et al. · Institutional Repository of Xi'an Institute of Optics and Fine Mechanics, Chinese Academy of Sciences (Xian Institute of Optics and Precision Mechanics) · 1987
PURPOSE:To obtain a distributed feedback semiconductor laser with good reproducibility and without increasing a threshold by a method wherein the reflectance of one end surface is predetermined to be or less than a specific percentage and the reflectance of the other end surface is predetermined to be or less than a specific percentage. CONSTITUTION:A mechanism which shifts the phase of a guided light is provided in a distributed feedback semiconductor laser. The product of a coupling coefficient and a resonator length is predetermined to be less than 2. The reflectance of one end surface and the reflectance of the other end surface are predetermined to be more than 5% and less than 15% and to be less than 2% respectively. For instance, an ordinary buried type laser is formed in such a manner that a stripe is so formed as to make the width of an active layer 4, 5mum in a phase shifting region at the center and 1mum in the other region. The length of the phase shifting region is predetermined to be 30mum so that the amount of phase shift is to be reduced to a quarter. A laser is cut out of the wafer like this so as to have the resonator length of 150mum and the reflectance of nearly 0% is provided by cleaving the front and forming an inclined etched surface 8 on the back. In this case, the product of the coupling coefficient and the resonator length is estimated to be approximately
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ISHINO, MASATO, KITOH, MASAHIRO, OTSUKA, NOBUYUKI et al. · Institutional Repository of Xi'an Institute of Optics and Fine Mechanics, Chinese Academy of Sciences (Xian Institute of Optics and Precision Mechanics) · 1996
A distributed feedback semiconductor laser which includes a semiconductor substrate of a first conductive type; a semiconductor multi-layer structure provided on the semiconductor substrate and including an active layer for generating laser light; and a gain-coupled diffraction grating provided between the semiconductor substrate and the semiconductor multi-layer structure. The diffraction grating includes a plurality of curved projections periodically arranged at a surface of the semiconductor substrate and a quantum well light absorption layer for covering the plurality of curved projections. The quantum well light absorption layer includes a light absorption area having a first thickness at each border between two adjacent curved projections and a non-light absorption area having a second thickness which is smaller than the first thickness at a top of each of the curved projections. The light absorption area has a band gap which is narrower than a band gap of the active layer, and the non-light absorption area has a band gap which is wider than the band gap of the active layer.
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F. Dixon, M. Feng, N. Holonyak · Applied Physics Letters · 2010
Single longitudinal mode operation of an InGaP/GaAs/InGaAs quantum well heterojunction bipolar transistor laser is reported. A third order distributed feedback surface grating is fabricated in the top emitter AlGaAs confining layers using soft photocurable nanoimprint lithography. The device produces continuous wave laser operation with a peak wavelength λ=959.75 nm and threshold current IB=13 mA operating at −70 °C. For devices with cleaved ends a sidemode suppression ratio >25 dB has been achieved.
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MARUTANI YUKITOSHI, DOI MASATO · Institutional Repository of Xi'an Institute of Optics and Fine Mechanics, Chinese Academy of Sciences (Xian Institute of Optics and Precision Mechanics) · 1992
PURPOSE:To dominantly generate a gain-coupled type distributed feedback in a distributed-feedback semiconductor laser. CONSTITUTION:A recessed and protruding diffraction grating constitution in which grooves extended along a specific crystal orientation have been arranged and formed in parallel on a first guide layer 3 formed on a 100 crystal plane for a semiconductor substrate is formed. At least a second guide layer 5 and an active layer 6 are formed on its recessed and protruding face; the active layer 6 which is separated inside recessed parts or in which recessed parts or protruding parts are separated from each other is arranged.
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NODA SUSUMU, KOJIMA KEISUKE, TAI SHUICHI et al. · Institutional Repository of Xi'an Institute of Optics and Fine Mechanics, Chinese Academy of Sciences (Xian Institute of Optics and Precision Mechanics) · 1988
PURPOSE:To obtain a distributed feedback type semiconductor laser which can operate at a high output, has larger coupling constant and good sole mode property by specifying the mean thickness of a guide layer. CONSTITUTION:The compositions and the thicknesses of layers are fundamentally the same as those of a conventional example, but the mean thickness of a guide layer 7 is increased to 0.25-0.35mum as compared with the conventional one. In the principle of operation, when a current flows between electrodes 1 and 11, a light is generated in an active layer 5, confined in the active layers 5, 7 by upper and lower clad layers 8, 4, selectively amplified to the light of wavelength determined by the period of a diffraction grating provided in the layer 7 to generate a laser. When the mean thickness of the layer 7 is increased, most of the electric field in the laser is distributed in the layer 7. Thus, the rate of the electric field affected by Bragg's reflection by the diffraction grating is increased, and the value of the coupling constant is increased.
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KASUKAWA AKIHIKO, KASHIWA SUSUMU · Institutional Repository of Xi'an Institute of Optics and Fine Mechanics, Chinese Academy of Sciences (Xian Institute of Optics and Precision Mechanics) · 1987
PURPOSE:To be able to manufacture a distributed feedback semiconductor laser by an MOCVD method and to obtain the laser which can sufficiently perform a signal longitudinal and lateral mode operations with low threshold value by providing a waveguide layer formed on a current blocking layer with a smaller refractive index than that of an active layer and a second conductive type clad layer formed on the waveguide layer. CONSTITUTION:An etching stop layer 14 made of p-type GaInAsP (lambdag=1mum), a current blocking layer 15 made of an n-type Inp, and a current blocking layer 16 are sequentially laminated on an intermediate layer 13. A waveguide layer 17 made of a p-type GaInAsP (lambdag=1mum) is formed on a refractive index and the layer 16 exposed by a channel. A clad layer 18 made of a p-type InP by a series of growing process, and a cap layer 19 made of a p-type GaInAsP (lambdag=3mum) are sequentially laminated on the layer 17. A refractive index difference occurs between the inside the channel and the part except the inside, and a stable basic lateral mode operation can be achieved. Further, since the layers 15, 16 are disposed therein, it can be operated with low threshold current.
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HIRATA SHOJI · Institutional Repository of Xi'an Institute of Optics and Fine Mechanics, Chinese Academy of Sciences (Xian Institute of Optics and Precision Mechanics) · 1988
PURPOSE:To realize lambda/4 phase shift without changing an optical guide mechanism by forming a rib-shaped diffraction grating having a discontinuous section along the direction of an optical guide, reducing the thickness of guide layers on both sides of the discontinuous section and shaping stepped sections. CONSTITUTION:A clad layer 2, an active layer 3 and a guide layer 4 are epitaxial-grown onto the main surface of a semiconductor substrate 1 in succession, and a diffraction grating 5 having width W1 and uniform pitches along the direction of an optical guide is shaped on the surface of the guide layer 4. A flat discontinuous section, a phase shift region 12, is formed at the center of the diffraction grating 5 and flat surfaces on both sides of the region 12. Flat sections 14b shaping stepped sections of half the height D of the diffraction grating 5 are formed on both sides of the phase shift region 12. A clad layer 6 and a cap layer 7 are shaped onto the whole surface of such a guide layer 4, and electrodes 9, 10 are formed onto both surfaces.
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